Question

$K_a$ foe a weak acid HA is ${2\times 10}^{-5}$. What is the value of $K_b$ for $A^{-}$?

Answer 1

$ka-kb=kw={10}^{-14}$

$kb=\frac{{10}^{-14}}{2\times {10}^{-5}}=\frac{{10}^{-4}\times {10}^5}{2}=5\times {10}^{-10}$

$\therefore$ The value of $kb$ from $A$ is $5\times {10}^{-10}$